Embodiments of the present invention relate to a light guide device in a liquid crystal display (LCD).
It is known that a liquid crystal panel in a liquid crystal display is the component for displaying images; however, the liquid crystal panel itself can not emit light and thus a light source with sufficient luminance and uniform intensity has to be provided for the liquid crystal panel. At present, a backlight of side-emission type is usually used to provide the light demanded by the liquid crystal display.
As shown in FIG. 1 and FIG. 2, a conventional backlight of side-emission type 100 comprises a light source 101, a reflective cover 102, a light guide plate 103, a bottom reflective film 104, a side reflective film 105, and optical sheets 106. Specifically, in operation, light is emitted from the light source 101, and collected by the reflective cover 102, and enter the light guide plate 103. Total reflection of the light in the light guide plate 103 is mostly prevented with the dot patterns formed on the bottom surface of the light guide plate 103 or other structures with similar function, and thus the light is scattered evenly. Then, the scattered light is emitted at the light exit surface of the light guide plate 103 after multiple reflections and refractions in the light guide plate 103 and finally modulated by the optical sheets 106 so as to provide a surface light source with uniform luminance. However, the conventional backlight of side-emission type has some disadvantages.
The light emitted from the light source enters into the light guide plate 103 through the side surfaces 110, 111 of the light guide plate 103 (shown in FIG. 2), and thus the light is modulated by the dot patterns mainly along the vertical direction, and it is difficult to control the luminance uniformity along the horizontal direction.
In addition, a cold cathode fluorescent lamp (CCFL) is usually used as for the light source 101 in the backlight of side-emission type 100, but a cold cathode fluorescent lamp has a disadvantage of non-uniform luminance. FIG. 3 shows the luminance distribution that occurs on both sides of the light guide plate 103. As shown in FIG. 3, a dim region that has a relatively less luminance than the normal regions on the light guide plate 103 is generated at each of the four corners of the backlight (in the luminance distribution shown in FIG. 3, a bright region is shown by a heavy tone and a dim region is shown by a light tone), and it is difficult to eliminate the dim regions.